Yellow Rainbowfish ~ Melanotaenia herbertaxelrodi

The Yellow Rainbowfish is a brilliantly colored freshwater species admired for its golden-yellow body, subtle iridescent sheen, and elegant, deep-bodied profile. Native to the slow-flowing tributaries and rainforest streams of Papua New Guinea, this species is prized by aquarists for its peaceful nature, energetic swimming patterns, and stunning coloration that intensifies with good diet and clean water. As with most rainbowfish, males develop deeper bodies and stronger hues, while females exhibit softer tones that contribute to the beauty of the entire school.

• Size: 3.5-4.5 inches

• Lifespan: 5-8 years

• Temperament: Peaceful, active

• Group/Solitary: Best kept in groups of 6+

• Food: Omnivorous, quality flakes or micro-pellets, spirulina foods, live/frozen offerings including brine shrimp, bloodworms, and daphnia

• Water Requirements: 74-82°F, pH 6.5-8.0, moderate hardness

Yellow Rainbowfish thrive in large, well-oxygenated aquariums with open swimming space and lush plants around the edges. Their active schooling behavior becomes far more pronounced and visually impressive when kept in groups of six or more, reducing stress and encouraging natural social dynamics. A varied diet rich in spirulina and protein-based foods is essential for maintaining their vivid golden coloration and overall health. They coexist well with other peaceful, fast-moving species of similar size, but should not be housed with overly aggressive or nippy tank mates.

In the wild, Yellow Rainbowfish inhabit clear freshwater streams and small rivers bordered by dense forest growth. These ecosystems provide filtered light, submerged vegetation, and clean, oxygen-rich water that supports robust schooling life. Seasonal rainfall patterns influence water clarity and flow, shaping their natural adaptability and tolerance for a range of stable aquarium conditions.

Fun Fact: When sunlight or aquarium lighting strikes their scales at the right angle, Yellow Rainbowfish produce a shimmering metallic glow that shifts subtly as they move, making a school appear like a sweeping band of liquid gold.